Continuously advancing networks enable a variety of services to be developed. Among these services services are various services which have been implemented to be used by a subscriber when desired, such as a video-on-demand, for example. These services are also called services-on-demand. The basic structure of this kind of service is that the subscriber uses his/her equipment to send commands via a network to a server offering the service and the server acts according to the commands received and, for example, starts to transmit a selected video in a service stream from the server to the subscriber equipment via the network. The quality of the service, the protocol used and the bandwidth the service requires in the network are negotiated between the server and the end customer and, on the basis of the negotiations, a pipe is formed via which the service stream is transmitted.
A problem with the above described arrangement is that the network has no means to control the service stream. The traffic management in the network is totally dependent on solutions made by server vendors.